Process for improving stain resistance and lightfastness of carpet yarn

ABSTRACT

Disclosed is a method for dyeing solution dyed bulk continuous filament (BCF) fibers. The BCF fibers are twisted together to form a 2 or more ply strand prior to dyeing. After twisting the fibers together, the fiber is preferably spaced dyed to provide a multi-colored pattern along the length of the strand. Following the space dyeing step, the strand is heat set.

TECHNICAL FIELD

This invention relates generally to dyed textile fabrics. More particularly, the invention relates to processes for dying long striations of color onto solution dyed yarn and while maintaining stain resistance and lightfastness of the yarn.

BACKGROUND OF THE INVENTION

Nylon carpet and other fabrics made from synthetic yarns are commonly colored using one of several known processes, including dyeing with acid dyes, pre-metalized acid dyes, disperse dyes, and fiber-reactive dyes. For example, “space dyeing” is a dyeing process by which dyes of particular colors are applied intermittently along the length of the yarn, thus creating differently-colored “spaces” in the yarn. In the conventional space dyeing process, colorless white yarn is colored by applying multiple colors along the length of each strand of yarn. Those colors may or may not repeat after a fixed interval. Thus, the space dyeing process is used to give yarn a unique, multi-colored effect. When space dyed yarns are used to form fabric, patterns can emerge depending on the length and variation of each color block. The multi-colored effect of spaced-dyed yarn is desirable for many reasons, including aesthetics as well as its ability to hide defects, stains, etc. However, dye applied in the space dyeing process is not applied throughout the yarn. Even after the dyeing process is complete, certain portions (typically not visible to the human eye) remain un-dyed. These un-dyed portions allow for discoloration (i.e., staining, fading, etc.) to occur.

Another way to obtain color in nylon and other types of yarn is through a yarn manufacturing process that is somewhat misleadingly called “solution dyeing.” The solution dye process adds color pigments into the polymer during the melt spinning process as the yarn is being made. The color applied by solution dyeing yarns is consistent along the entire length of the strand of yarn without variation or pattern. Since the pigment or colorant is included as part of the yarn itself, there are no un-dyed portions in solution dyed yarns. As such, solution dyed yarns are much more resistant to stains and aggressive cleaning than yarns that are colored by the application of dyes. However, since color is formed as part of solution dyed yarn, these yarns do not have the multi-colored effect of spaced dyed yarn that is often desired. The aesthetics of carpet made from solution dyed yarn is often limited to solid colored yarn or “barber pole” yarn comprised of two contrastingly-colored singles that are twisted together. The solution dye process is a low cost operation. However, in order to meet consumer demand, the carpet mill may need to keep a costly inventory of colored yarns produced by the solution dye process. Variable production demands and large inventory costs can impact inventory flexibility. Typically, producers limit inventory of solution dyed yarn in order to accommodate changing tastes, changing production demands, and reduce inventory costs. However, this limits color availability for carpets employing solution dyed yarn and may cause delays in delivering carpet of a particular color to a customer if the desired color of yarn is not on hand.

What is needed, therefore, is a method for dyeing carpet that provides the stain resistance and lightfastness of solution dyed yarn while allowing for the color variation of space dyed yarn.

NOTES ON CONSTRUCTION

The use of the terms “a”, “an”, “the” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic.

The use of any and all examples or exemplary language (e.g., “such as” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiment thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity.

BRIEF SUMMARY OF THE INVENTION

The above and other needs are met by a method for dyeing carpet fibers comprising the following steps, carried out in the following order: providing two or more solution dyed bulk continuous filament (BCF) fibers, twisting the two or more BCF fibers to form a 2 or more ply strand, space dyeing the twisted non-heat set strand, and heat setting the twisted space dyed strand.

In order to facilitate an understanding of the invention, the preferred embodiments of the invention, as well as the best mode known by the inventors for carrying out the invention, are provided in the detailed description below. It is not intended, however, that the invention be limited to the particular embodiments described herein. Therefore, the scope of the invention contemplated by the inventors includes all equivalents of the subject matter described herein, as well as various modifications and alternative embodiments such as would ordinarily occur to one skilled in the art to which the invention relates. The inventors expect skilled artisans to employ such variations as seem to them appropriate, including the practice of the invention otherwise than as specifically described herein. In addition, any combination of the elements and components of the invention described herein in any possible variation is encompassed by the invention, unless otherwise indicated herein or clearly excluded by context.

DETAILED DESCRIPTION OF THE INVENTION

Provided by the present invention is a method for dyeing carpet fibers that may be used in forming carpet that has the stain resistance and lightfastness of carpet made with solution dyed yarn while also allowing for the color variation of carpet made with space dyed yarn. According to an embodiment of the invention, the method comprises an initial step of providing two or more solution dyed bulk continuous filament (BCF) fibers. These BCF fibers are preferably formed from yarns formed from a cationic-based pigmented polymer, such as polyamide. For example, in some embodiments, a suitable fiber is nylon type 6 fiber. In other embodiments, a suitable fiber is nylon type 6.6 fiber. The BCF fibers are twisted or cabled to form a 2 or more ply strand of fiber. The twist level provided should be suitable for the wear performance and style of carpet. This twisting step is carried out on conventional twisting equipment. For example, in certain embodiments, the fibers are twisted using a direct cable machine, such as CBT CD/DT 460 model cabler by ICBT.

Next, the cabled (but not heat set) yarn is spaced dyed. Cationic-based polymers are inherently stain resistant to acid-type stains and can be dyed with cationic dyes. However, when dyed with cationic dyes, these polymers have poor lightfastness. For that reason, it is preferable to use a pre-metalized dye in this space dyeing step. Preferably, this space dyeing step occurs on a continuous yarn space dye machine using a dye having a pH level of 2.5 to 3.0. For example, in one exemplary embodiment, pre-metallized dye is applied using a continuous yarn space dyeing apparatus, such as the Belmont MDS III Continuous Yarn Dyeing System. In certain preferred embodiments, two or more different colors are applied along the length of the strand during this dyeing step. In certain embodiments, the colors may be repeated on the same fiber strand. Advantageously, up to 100% of the yarn can be dyed using multiple colors and in varying lengths (including long and/or short portions) along its length using the method described above.

Conventionally, to achieve the above-described style in carpet, yarn was twisted, heat set, and then space dyed. If the heat set method utilized saturated steam, such as with a Superba Heat Set Machine, then the resulting yarn would stain easily and peroxide-based cleaners would remove color. If the heat set method utilized superheated steam, such as with a GVA model heat setting machine by Power-Heat-Set GmbH, obtaining level dyeing was not possible due to the stain-resistant properties imparted by the heat setting machine. The presently-disclosed process allows the dye to be applied on the non-heat set yarn while also allowing the dye process to be controlled. The dyed yarn is then heat set in order to achieve the desired stain resistance, lightfastness and cleaning properties.

After being exposed to the dye, the yarn is transported through a series of steamers to complete the dye fixation process. For example, in one embodiment, dye is steam set using steam that is at least 98° C. atmospheric temperature for at least 4 minutes. After being steam fixed, the yarn is washed and extracted using a hot water wash that is at least 63° C. to remove any chemical residue. Then the yarn is dried. Preferably, the yarn is dried in a conventional drying apparatus. In some cases, the drying apparatus is part of the space dyeing apparatus, which is the case with the Belmont system discussed above. Preferably, the drying apparatus is set to a minimum temperature of 138° C. for at least 4 minutes.

Next, the yarn is heat set in an atmospheric-controlled climate chamber, such as a continuous heat setting apparatus. For example, in one embodiment, a suitable heat setting apparatus may include Power-Heat-Set GVA 5009 ECO. In preferred embodiments, the yarn is held in this chamber, which preferably has a dew point temperature between 88° C. and 96° C. The temperature setting of the chamber is then set above the dew point temperature to ensure that the yarn is thoroughly dried. For example, for nylon type 6, the chamber is preferably set between 180° C. and 202° C.±3° C. from the set point (i.e., between 177° C. and 205° C.). In another example, for nylon type 6.6, the chamber is preferably set between 196° C. and 212° C.±3° C. from the set point (i.e., between 193° C. and 215° C.). Preferably, the dwell time is between 45 seconds and 65 seconds.

The above-described process provides unexpected improvements in lightfastness and stain resistance. The dyes can be applied evenly on the non-heat set yarn so that it is controllable for depth of shade in the continuous space dye process. The yarn is then heat set by superheated steam in the GVA 5009 ECO heat setting machine or another similar machine. During this process, the yarn forms a capillary oxide film on its surface. This film protects both the solution dye color and the space dye color from stains and light fading.

Finally, after the heat setting process is complete, the yarn can be tufted in the desired carpet style. In certain embodiments, the yarn forms 100% of the face fiber of the carpet. In other embodiments, the yarn is combined with other cationic-based solution dyed fibers to form the face fiber of the carpet. Advantageously, a carpet formed from carpet fibers produced according to the above-described method may be provided with an aesthetic having a striation or a multi-color effect. Also, the resulting carpet may be aggressively cleaned (e.g., using peroxide-based cleaners) without a significant change in its color appearance.

Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments thereof, as well as the best mode contemplated by the inventor of carrying out the invention. The invention, as described and claimed herein, is susceptible to various modifications and adaptations as would be appreciated by those having ordinary skill in the art to which the invention relates. 

What is claimed is:
 1. A method for dyeing carpet fibers comprising the following steps, carried out in the following order: A. providing two or more solution dyed bulk continuous filament (BCF) fibers; B. twisting the two or more BCF fibers to form a 2 or more ply strand; C. space dyeing the twisted non-heat set strand; and D. heat setting the twisted space dyed strand.
 2. The method of claim 1 wherein the BCF fibers are formed using a cationic-based polymer.
 3. The method of claim 2 wherein the BCF fibers are formed using cationic-based polyamide polymer.
 4. The method of claim 1 wherein a pre-metalized dye is applied during the space dyeing step (i.e., Step C).
 5. The method of claim 4 wherein the pre-metalized dye has a pH level of 2.5 to 3.0.
 6. The method of claim 1 further comprising applying two or more different colors along the length of the strand during dyeing step (i.e., Step C).
 7. The method of claim 1 wherein the space dyed strand is heat set in an atmospheric controlled climate to between 88° C. and 96° C. dew point temperature.
 8. The method of claim 1 wherein the BCF fibers are formed from nylon type
 6. 9. The method of claim 8 wherein the twisted space dyed strand is heat set using a temperature set point of 177° C. to 205° C.
 10. The method of claim 1 wherein the BCF fibers are formed from nylon type 6.6.
 11. The method of claim 10 wherein the twisted space dyed strand is heat set using a temperature set point of 193° C. to 215° C.
 12. The method of claim 1 wherein a heat setting dwell time is between 45 and 65 seconds.
 13. The method of claim 1 wherein the two or more BCF fibers are twisted using a direct cable machine, the strand is spaced dyed using a continuous yarn space dyeing apparatus, or the strand is heat set using a continuous heat setting apparatus.
 14. The method of claim 1 further comprising the following steps, carried out in the following order after Step C and before Step D: E. washing the space dyed and heat set strand; and F. steam setting the washed strand.
 15. The method of claim 9 wherein the space dyed and heat set strand is washed at Step E in water having a temperature of at least 63° C.
 16. The method of claim 10 wherein the washed strand is steam set at Step F in steam to a temperature of at least 98° C. over a water bath that is heated to at least 100° C.
 17. The method of claim 10 wherein the washed strand is steam set at Step F for at least 4 minutes.
 18. A fabric comprising: a solution dyed strand formed from two or more bulk continuous filament (BCF) fibers twisted together; and a dye applied to the solution dyed strand after the strand has been formed.
 19. The fabric of claim 18 wherein the dye comprises two or more colors applied to the strand;
 20. The fabric of claim 18 wherein the two or more colors repeat on the strand. 